In an electrophotography technology in recent years, a low-energy fixing device (low temperature fusing) is under development for reducing electrical power consumption and high-speed printing since energy conservation is widely requested. However, there was a problem that thermal stability of a toner for electrostatic image development (also referred to simply as a “toner” hereinafter) was reduced as the low temperature fusing was developed and heat resistant storage of the toner during storage and transportation might become insufficient.
There was another problem that since a component such as a colorant or a release agent is exposed on a surface of the toner, it was difficult to render stable electrostatic chargeability to the toner for a long time. To solve these problems a technique to improve toner performance using a core-shell structure, in which a surface of the toner is covered with a resin, has been proposed until now (see Patent Literatures 1 and 2, for example).
On the other hand, it has been sought a departure from high environmental load-materials derived from petroleum that emits green house gases such as a carbon dioxide, by putting the Law Concerning the Promotion of Procurement of Eco-friendly Goods and Services by the State and Other Entities (Law on promoting green purchasing), for example, into effect. Consequently, it is now requested to use biomass resources as low environmental load materials instead of the materials derived from petroleum. Patent Literatures 3 to 5, for example, disclose such biomass resources.
In particular, Patent Literature 5 discloses a technique to produce a binder resin containing a compound having a furfural structure form biomass as a binder resin that is excellent to render low temperature fusing property and storability to the toner.
However, there is a possibility that, when the compound having a furfural structure is used for a binder resin, the binder resin may be colored or oxidized into brown. In addition, the binder resin tends to interact with moisture in the air under high temperature and high humidity conditions and that may cause a fluctuation of amount of electrostatic charge (charge amount) in accordance with environmental fluctuation. Therefore, the binder resin is not suitable for use of a color toner since it may interrupt good coloring of the color toner.